Multi-Stage Thermal Storage Tank for Constant Temperature Discharge
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Solution Overview
Problem
Existing thermal storage tanks of the dual thermocline type face challenges in maintaining constant fluid temperatures during discharge, leading to degraded performance and flexibility issues, particularly in varying solar radiation conditions, which affects the efficiency and stability of systems like steam turbines.
Innovation Solution
A thermal storage tank design featuring multiple stages of solid matrix and liquid coolant with distributed liquid distributors allows for flexible injection of fluids at different heights based on temperature needs, enabling optimized operation and efficiency by creating multiple thermal pistons and zones for charging and discharging, and adaptable storage volume according to seasonal demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single tank with thermal stratification is used, then the number of components is reduced and control is simplified, but the temperature at the outlet cannot be kept constant throughout the discharge phase
Solution Approach 1:
The single tank is segmented into multiple stages with distinct functional zones: a hot zone at the top, a cold zone at the bottom, and intermediate zones with solid matrix layers. This segmentation allows different regions to perform different functions (storage, heat transfer, temperature stabilization), enabling constant outlet temperature while maintaining a single-tank configuration.
Solution Approach 2:
Solid matrix materials (such as rocks or ceramic elements) are introduced as intermediary substances between the hot and cold fluid zones. These solid matrices act as thermal buffers that stabilize temperature transitions, preventing direct mixing of hot and cold fluids and maintaining constant outlet temperature during discharge.
2Use of energy by moving object
If fluid velocity is increased to improve heat transfer, then heat transfer efficiency improves, but natural convection movements occur causing temperature inhomogeneity
Solution Approach 1:
Different velocity regimes are applied in different zones of the tank. In the solid matrix layers, very low fluid velocities (a few mm/s) are maintained to prevent convection and maintain temperature uniformity. In the liquid-only zones (top and bottom), higher velocities can be used for efficient heat transfer without causing instability in the solid matrix regions.
Solution Approach 2:
The solid matrix provides a porous structure that allows controlled fluid flow while maintaining thermal stability. The porous material enables heat transfer through its surface area while its physical structure prevents bulk fluid movement and natural convection, allowing efficient heat transfer without temperature inhomogeneity.
3Reliability
If the storage tank is dimensioned for equinox performance, then it meets seasonal requirements, but it cannot adapt to varying solar radiation conditions throughout the year
Solution Approach 1:
The tank operates dynamically by adjusting the active storage volume and fluid circulation patterns according to seasonal demands. During periods of high solar radiation, the entire tank volume is utilized with full circulation. During low-radiation periods, only the necessary portions are activated, allowing the system to adapt to varying conditions while maintaining reliable performance.
Solution Approach 2:
The system changes operational parameters (fluid flow rates, active storage volume, heat transfer coefficients) based on seasonal requirements and solar radiation levels. This allows the same physical tank to optimize its performance for different operating conditions, maintaining reliability across varying environments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design ensures constant temperature control, enhances operational flexibility, and improves energy efficiency by allowing simultaneous use of stored heat for multiple systems and adapting storage capacity to seasonal variations, reducing energy losses and maintaining system performance across different solar radiation levels.
Implementation Method 1
Heat storage can typically be achieved either as sensible energy (by varying the temperature level of a solid or liquid storage material)
Implementation Method 2
in the event of temperature inhomogeneity in a transverse plane. These movements of natural convection ensure a homogenization of the temperature
Implementation Method 3
the repository is characterized by a hot zone at the top of the tank, a cold zone at the bottom and a transition zone between the two zones called the thermocline
Data Source
Figure 1
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AI summary
Disclosed is a heat storage tank comprising a shell (2) with a longitudinal axis (X) filled with a heat-transfer liquid and solid heat-storage elements, a first longitudinal end having top means (DS) for collecting and supplying a liquid at a first temperature, and a second longitudinal end having bottom means (Dl) for collecting and supplying a liquid at a second temperature, in which said solid heat-storage elements are distributed across a plurality of beds (TH1, TH2, TH3) stacked along the longitudinal axis (X) and separated by a liquid layer (L1, L2, L3), the liquid being suitable for circulating between the first longitudinal end and the second longitudinal end. The tank also comprises fluid collection and distribution means (D2.1, D2.2, D3.1, D3.2) arranged in the liquid layers (L1, L2, L3).